Sea levels likely to rise much faster than was predicted

A A A

Global warming is causing the Greenland ice cap to disintegrate far faster than anyone predicted. A study of the region's massive ice sheet warns that sea levels may - as a consequence - rise more dramatically than expected.

Scientists have found that many of the huge glaciers of Greenland are moving at an accelerating rate - dumping twice as much ice into the sea than five years ago - indicating that the ice sheet is undergoing a potentially catastrophic breakup.

The implications of the research are dramatic given Greenland holds enough ice to raise global sea levels by up to 21ft, a disaster scenario that would result in the flooding of some of the world's major population centres, including all of Britain's city ports.

Satellite measurements of the entire land mass of Greenland show that the speed at which the glaciers are moving to the sea has increased significantly over the past 10 years with some glaciers moving three times faster than in the mid-1990s.

Scientists believe that computer models of how the Greenland ice sheet will react to global warming have seriously underestimated the threat posed by sea levels that could rise far more quickly than envisaged.

The latest study, presented at the American Association for the Advancement of Science, in St Louis, shows that rather than just melting relatively slowly, the ice sheet is showing all the signs of a mechanical break-up as glaciers slip ever faster into the ocean, aided by the "lubricant" of melt water forming at their base.

Eric Rignot, a scientist at the Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, said that computer models used by the UN's International Panel on Climate Change have not adequately taken into account the amount of ice falling into the sea from glacial movements.

Yet the satellite study shows that about two-thirds of the sea-level rise caused by the Greenland ice sheet is due to icebergs breaking off from fast-moving glaciers rather than simply the result of water running off from melting ice.

"In simple terms, the ice sheet is breaking up rather than melting. It's not a surprise in itself but it is a surprise to see the magnitude of the changes. These big glaciers seem to be accelerating, they seem to be going faster and faster to the sea," Dr Rignot said.

"This is not predicted by the current computer models. The fact is the glaciers of Greenland are evolving faster than we thought and the models have to be adjusted to catch up with these observations," he said.

The Greenland ice sheet covers an area of 1.7 million sq km - about the size of Mexico - and, in places, is up to 3km thick. It formed over thousands of years by the gradual accumulation of ice and snow but now its disintegration could occur in decades or centuries.

Over the past 20 years, the air temperature of Greenland has risen by 3C and computer models suggested it would take at least 1,000 years for the ice sheet to melt completely. But the latest study suggests that glaciers moving at an accelerating rate could bring about a much faster change.

"The behaviour of the glaciers that dump ice into the sea is the most important aspect of understanding how an ice sheet will evolve in a changing climate," Dr Rignot said. "It takes a long time to build and melt an ice sheet but glaciers can react quickly to temperature changes. Climate warming can work in different ways but, generally speaking, if you warm up the ice sheet, the glacier will flow faster," he said.

The ice "balance sheet" of Greenland is complex but - in simple terms - it depends on the amount of snow that falls, the amount of ice that melts as run-off and the amount of ice that falls directly into the sea in the form of icebergs "calving" from moving glaciers.

Satellites show that the glaciers in the south of Greenland are now moving much faster than they were 10 years ago. Scientists estimate that, in 1996, glaciers deposited about 50 cubic km of ice into the sea. In 2005 it had risen to 150 cubic km of ice.

Details of the latest study, published in the journal Science, show that Greenland now accounts for an increase in global sea levels of about 0.5 millimetres per year - compared to a total sea level rise of 3mm per year.

When previous studies of the ice balance are taken into account, the researchers calculated that the overall amount of ice dumped into the sea increased from 90 cubic km in 1996 to 224 cubic km in 2005.

Dr Rignot said that there are now signs that the more northerly glaciers of Greenland are beginning to adopt the pattern of movements seen by those in the south. "The southern half of Greenland is reacting to what we think is climate warming. The northern half is waiting, but I don't think it's going to take long," he said.

Have you tried new the Independent Digital Edition apps?
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Recruitment Genius: Bookkeeper / Office Co-ordinator

£9 per hour: Recruitment Genius: This role is based within a small family run ...

Recruitment Genius: Designer - Print & Digital

£28000 - £32000 per annum: Recruitment Genius: This Design and marketing agenc...

Recruitment Genius: Quantity Surveyor

£46000 per annum: Recruitment Genius: This property investment firm are lookin...

Recruitment Genius: Telesales / Telemarketing Executive - OTE £30k / £35k plus

£18000 - £35000 per annum: Recruitment Genius: This company specialises provid...

Day In a Page

The difference between America and Israel? There isn’t one

The difference between America and Israel? There isn’t one

Netanyahu knows he can get away with anything in America, says Robert Fisk
Families clubbing together to build their own affordable accommodation

Do It Yourself approach to securing a new house

Community land trusts marking a new trend for taking the initiative away from developers
Head of WWF UK: We didn’t send Cameron to the Arctic to see green ideas freeze

David Nussbaum: We didn’t send Cameron to the Arctic to see green ideas freeze

The head of WWF UK remains sanguine despite the Government’s failure to live up to its pledges on the environment
Author Kazuo Ishiguro on being inspired by shoot-outs and samurai

Author Kazuo Ishiguro on being inspired by shoot-outs and samurai

Set in a mythologised 5th-century Britain, ‘The Buried Giant’ is a strange beast
With money, corruption and drugs, this monk fears Buddhism in Thailand is a ‘poisoned fruit’

Money, corruption and drugs

The monk who fears Buddhism in Thailand is a ‘poisoned fruit’
America's first slavery museum established at Django Unchained plantation - 150 years after slavery outlawed

150 years after it was outlawed...

... America's first slavery museum is established in Louisiana
Kelly Clarkson: How I snubbed Simon Cowell and become a Grammy-winning superstar

Kelly Clarkson: How I snubbed Simon Cowell and become a Grammy-winning superstar

The first 'American Idol' winner on how she manages to remain her own woman – Jane Austen fascination and all
Tony Oursler on exploring our uneasy relationship with technology with his new show

You won't believe your eyes

Tony Oursler's new show explores our uneasy relationship with technology. He's one of a growing number of artists with that preoccupation
Ian Herbert: Peter Moores must go. He should never have been brought back to fail again

Moores must go. He should never have been brought back to fail again

The England coach leaves players to find solutions - which makes you wonder where he adds value, says Ian Herbert
War with Isis: Fears that the looming battle for Mosul will unleash 'a million refugees'

The battle for Mosul will unleash 'a million refugees'

Aid agencies prepare for vast exodus following planned Iraqi offensive against the Isis-held city, reports Patrick Cockburn
Yvette Cooper: We can't lose the election. There's too much on the line

Yvette Cooper: We can't lose the election. There's too much on the line

The shadow Home Secretary on fighting radical Islam, protecting children, and why anyone in Labour who's thinking beyond May must 'sort themselves out'
A bad week for the Greens: Leader Natalie Bennett's 'car crash' radio interview is followed by Brighton council's failure to set a budget due to infighting

It's not easy being Green

After a bad week in which its leader had a public meltdown and its only city council couldn't agree on a budget vote, what next for the alternative party? It's over to Caroline Lucas to find out
Gorillas nearly missed: BBC producers didn't want to broadcast Sir David Attenborough's famed Rwandan encounter

Gorillas nearly missed

BBC producers didn't want to broadcast Sir David Attenborough's famed Rwandan encounter
Downton Abbey effect sees impoverished Italian nobles inspired to open their doors to paying guests for up to €650 a night

The Downton Abbey effect

Impoverished Italian nobles are opening their doors to paying guests, inspired by the TV drama
China's wild panda numbers have increased by 17% since 2003, new census reveals

China's wild panda numbers on the up

New census reveals 17% since 2003